I'd you have time, check out the art or museum installation in the concourse; they always do a great job, and it's worth spending 10 minutes exploring.
My favorite foods in terminal 3: Andale and Firewood in the food court, Gordon Biersch if you are stuck by Gate 74, brand new good court by Gate 62 with Urban Tortilla and Klein's deli.
For quicker service at the United Premier lobby, go to the left end where all the agents are. If it's busy you may be waiting a while at the United.com bag check section.
Gordon Biersch is the only real food near gates 70-75. Everything on the menu is available for take out. Takes half the time - food is good, but service is slow.